A layer of insulation can reduce the rate of heat transfer between an object and its environment. Insulation can be used to help maintain the temperature of an object in hot or cold environments, or to allow safe handling of a hot or cold object. For example, insulation for an oil pipeline may promote free flow of oil at higher than ambient temperatures, and may also help pipeline workers avoid discomfort or burns.
In addition to reducing heat transfer, many types of insulation also prevent or reduce moisture transfer between the insulated object and its environment, and some types of insulation may even promote the development of moisture on the object. Trapped moisture between the insulation and the object may cause corrosion at the interface of a metal surface of the object and the insulation, and may also reduce the effectiveness of the insulation. Insulation that traps or promotes moisture near an object may also carry the moisture to other parts of the insulated object, causing corrosion to spread rapidly. Additionally, many types of insulation may release chlorides into a trapped moisture layer, causing further pitting, corrosion, and/or cracking.
Corrosion under insulation (“CUI”) as described above may become particularly severe in circumstances where it is difficult or costly to detect corrosion, or to inspect an object covered by insulation. In the refining and chemical industries, where insulated pipes are used, a large percentage of leaks and piping maintenance costs may be related to CUI.